The present invention relates to the art pertaining to the moisturizing or conditioning of whole tobacco stems.
The relatively high cost of the tobacco components for smoking articles renders it desirable to fully utilize all of the tobacco leaf including the stems and veins of the leaf. Exemplary of prior patents disclosing processes for converting tobacco stems to usable products are U.S. Pat. Nos. 3,204,641 to Jones; 3,690,328 to Quarenghi; and 3,734,104 to Buchanan et al.
As used in the present disclosure, the term "stem" shall include both the stem as such, as well as the veins separable from the remainder of the tobacco leaf.
Typically, the prior art processes commence by moisturizing the stems to prepare the stems for rolling. The prior art, which will be specifically compared to the present invention, moisturizes the stems prior to rolling by applying water and steam to the stems. The water and steam are normally applied separately and directly to the stems. The subsequent rolling process opens the structure of the stem allowing further moisturization and expansion of the rolled stem subsequent to its comminution into a plurality of particles. It has also been discovered that the cellular structure of whole tobacco stems can be opened thermally by the simultaneous application of water and steam to whole tobacco stems.
Irrespective of the means used to open the cellular structure of the whole tobacco stems, the characteristics of the final product are significantly affected by the moisture content of the stems during comminution and expansion. While different processes may utilize stems at various total moisture contents, the processes are exceptionally responsive to seemingly minor variations in moisture content either from stem to stem or throughout the cross-section of the respective stems.
Moisture content significantly affects the mechanical properties of the stems and, therefore, their response to any mechanical process, for example, the comminution of the stems to particles.
In addition, moisture content can also affect the expansion of the particles. Particles having moisture contents outside the desired range of moisturization may, at least partially, contract after expansion, thereby reducing the cost effectivness of the utilization of such tobacco products.
Most commercial processes expanding tobacco stems achieve moderate success in communicating and expanding whole tobacco stems; however, the prior art processes are significantly improved by process steps that moisturize whole tobacco stems to a substantially uniform moisture content. The uniformity of moisturization enhances process performance by allowing such processes to be adjusted to optimal process parameters without concern for wide variations in moisture content that place significant portions of the stems outside the desired range of operation.
The fact that processes for utilization of tobacco stems involve millions of pounds of input material and product makes uniformity of moisturization commercially significant, since even minor improvements in process performance result in significant economic benefits.
The volume of material treated in such processes places constraints on the moisturization processes. It is desirable to treat the stems on a continuous basis, or, if continuity is not possible, with interruptions to continuity being as short as possible. Prior art processes attempt to achieve uniformity of moisturization by lengthy (e.g., 30 minutes) equilibration or bulking steps. The length of such steps seriously reduces the commercial viability of such processes.
Non-uniform moisturization of whole tobacco stems in processes for expanding the stems normally results in two serious process effects.
First, the generation of increased amounts of fine particles or meal occur during communication of the stems. This undesirable by-product can be utilized in other tobacco reclamation processes, but such materials cannot be directly incorporated into smoking articles and thus further processing costs are incurred. Again, the magnitude of the input materials makes significant by-product generation economically burdensome and reduces the cost effectiveness of stem expansion processes.
Second, the stems may incompletely expand or expand and then at least partially contract. Either of those two effects reduces the cost effectiveness of such processes.
Therefore, it is the primary object of the present invention to uniformly moisturize whole tobacco stems throughout the cross-section of the respective stems and from stem to stem.
It is an additional object of the invention to provide uniformly moisturized tobacco stems that can be comminuted without generation of excessive amounts of particulate fines or meal.
It is another object of the invention to produce uniformly moisturized whole tobacco stems suitable for comminution without the necessity for lengthly soaking or bulking steps.
It is also an object of this invention to condition whole tobacco stems to the extent that rolling or crushing of the stems is not necessarily required prior to comminution, but the stem conditioning of this invention can be utilized prior to rolling.
Further objects and advantages of the invention will be set out in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.